linux-kernel - [PATCH v2 7/8] scsi: sr: workaround VMware ESXi cdrom emulation bug

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Date:   Wed, 23 Oct 2019 14:52:46 +0200
From:   Michal Suchanek <msuchanek@...e.de>
To:     linux-scsi@...r.kernel.org
Cc:     Michal Suchanek <msuchanek@...e.de>,
        Jonathan Corbet <corbet@....net>, Jens Axboe <axboe@...nel.dk>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Eric Biggers <ebiggers@...gle.com>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Benjamin Coddington <bcodding@...hat.com>,
        Hannes Reinecke <hare@...e.com>,
        Omar Sandoval <osandov@...com>, Ming Lei <ming.lei@...hat.com>,
        Damien Le Moal <damien.lemoal@....com>,
        Bart Van Assche <bvanassche@....org>,
        Tejun Heo <tj@...nel.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH v2 7/8] scsi: sr: workaround VMware ESXi cdrom emulation bug

The WMware ESXi cdrom identifies itself as:
sr 0:0:0:0: [sr0] scsi3-mmc drive: vendor: "NECVMWarVMware SATA CD001.00"
model: "VMware SATA CD001.00"
with the following get_capabilities print in sr.c:
        sr_printk(KERN_INFO, cd,
                  "scsi3-mmc drive: vendor: \"%s\" model: \"%s\"\n",
                  cd->device->vendor, cd->device->model);

So the model looks like reliable identification while vendor does not.

The drive claims to have a tray and claims to be able to close it.
However, the UI has no notion of a tray - when medium is ejected it is
dropped in the floor and the user must select a medium again before the
drive can be re-loaded.  On the kernel side the tray_move call to close
the tray succeeds but the drive state does not change as a result of the
call.

The drive does not in fact emulate the tray state. There are two ways to
get the medium state. One is the SCSI status:

Physical drive:

Fixed format, current; Sense key: Not Ready
Additional sense: Medium not present - tray open
Raw sense data (in hex):
        70 00 02 00 00 00 00 0a  00 00 00 00 3a 02 00 00
        00 00

Fixed format, current; Sense key: Not Ready
Additional sense: Medium not present - tray closed
 Raw sense data (in hex):
        70 00 02 00 00 00 00 0a  00 00 00 00 3a 01 00 00
        00 00

VMware ESXi:

Fixed format, current; Sense key: Not Ready
Additional sense: Medium not present
  Info fld=0x0 [0]
 Raw sense data (in hex):
        f0 00 02 00 00 00 00 0a  00 00 00 00 3a 00 00 00
        00 00

So the tray state is not reported here. Other is medium status which the
kernel prefers if available. Adding a print here gives:

cdrom: get_media_event success: code = 0, door_open = 1, medium_present = 0

door_open is interpreted as open tray. This is fine so long as tray_move
would close the tray when requested or report an error which never
happens on VMware ESXi servers (5.5 and 6.5 tested).

This is a popular virtualization platform so a workaround is worthwhile.

Signed-off-by: Michal Suchanek <msuchanek@...e.de>
---
 drivers/scsi/sr.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 4664fdf75c0f..8090c5bdec09 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -867,6 +867,7 @@ static void get_capabilities(struct scsi_cd *cd)
 	unsigned int ms_len = 128;
 	int rc, n;
 
+	static const char *model_vmware = "VMware";
 	static const char *loadmech[] =
 	{
 		"caddy",
@@ -922,6 +923,11 @@ static void get_capabilities(struct scsi_cd *cd)
 		  buffer[n + 4] & 0x20 ? "xa/form2 " : "",	/* can read xa/from2 */
 		  buffer[n + 5] & 0x01 ? "cdda " : "", /* can read audio data */
 		  loadmech[buffer[n + 6] >> 5]);
+	if (!strncmp(cd->device->model, model_vmware, strlen(model_vmware))) {
+		buffer[n + 6] &= ~(0xff << 5);
+		sr_printk(KERN_INFO, cd,
+			  "VMware ESXi bug workaround: tray -> caddy\n");
+	}
 	if ((buffer[n + 6] >> 5) == 0)
 		/* caddy drives can't close tray... */
 		cd->cdi.mask |= CDC_CLOSE_TRAY;
-- 
2.23.0